The present invention relates generally to vacuum die casting machines and, more particularly, to an improved vacuum valve for evacuating the die cavity prior to injection of a molten casting material into the cavity.
As is known in the vacuum die casting industry, the removal of air and other gasses from the die cavity prior to injection of a molten metal shot results in improved flow of the molten material into the die cavity which, in turn, produces a casting having improved grain structure and surface finish. Evacuation of the die cavity is generally accomplished by a venting device that is in fluid communication with the die cavity. Several different types of venting devices are disclosed by the following U.S. Pat. Nos.: 2,785,448; 2,867,869; 2,904,861; 3,070,857; 3,433,291; 4,027,726; 4,729,422; 4,779,666; 4,782,886; 4,809,767; 4,825,933; 4,832,109; and 5,101,882. While the above patents disclose venting devices that appear to perform satisfactorily for their intended purpose, designers are always striving to improve the art.